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Afocal NV - Eye Lens to Objective Distance

eyepieces NV
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#1 Jeff Morgan

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Posted 05 February 2020 - 12:48 AM

I have just acquired a Gary Russell 50mm Super Plossl to compare against my Tele Vue 55mm Plossl.

 

The GR50 has a Delrin body and a T2 thread on the eye lens end. A T2 to C connector from RAF Camera is used to make the connection with the NVD. Beautifully simple and easier to use than my TNVC adapter, so I hope the optics prove out.

 

Looking at the T2 connection, a thought occurred to me:

 

Could edge of field aberrations be reduced or eliminated using readily available T2 spacers to find an optimum spacing between eye lens and NVD objective lens?

 

 

Perhaps Tele Vue would have thought of that and dismissed the idea. Possible host eyepieces in the Tele Vue line-up are quite varied, yet the TNVC adapter has no provision for length (spacing) adjustment.

 

I think I will order some Baader T2 spacers from Agena Astro.

 

 

 


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#2 chemisted

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Posted 05 February 2020 - 07:53 AM

With the 65 mm Super Plossl from Gary Russell GeezerGazer evaluated a number of spacers.  When I bought it from Ray I settled on a 25 mm T-2 spacer and it works very well with my ENVIS objective.  The top of the Tele Vue 55 mm Plossl is an adjustable spacer as well.  I keep it screwed all the way in and have had excellent results with both my RC-10 and Sky 90 when used with reducers that eliminate the natural field curvature of those telescopes.

 

It will be fun to hear how the new Plossl performs!


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#3 Jeff Morgan

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Posted 05 February 2020 - 10:47 AM

The top of the Tele Vue 55 mm Plossl is an adjustable spacer as well.  

?

 

The top of mine screws off as a solid unit (I am referring to the DioptRX ring), but the ring itself does not adjust. 

 

I could give this a try an a spacing adjustment on the 55 Plossl, but there is a lot of play when the threads are loosened.



#4 chemisted

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Posted 05 February 2020 - 11:08 AM

?

 

The top of mine screws off as a solid unit (I am referring to the DioptRX ring), but the ring itself does not adjust. 

 

I could give this a try an a spacing adjustment on the 55 Plossl, but there is a lot of play when the threads are loosened.

That play is interesting.  I don't have any when I unscrew mine.  I got it in 2000 as part of my OGS RC-10 purchase.  I wonder if somehow tolerances have changed over the years . . .



#5 Peregrinatum

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Posted 05 February 2020 - 03:39 PM

Sounds good Jeff, looking forward to your report on the 50mm.  That RAF T2/Envis adapter sure makes life simple for afocal, and using T2 spacers to adjust the back focus seems just as easy..

 

The GR65mm SP is coming in on Friday, so thanks Ed for the 25mm spacer tip when using the Envis.




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